Known conventional retractable-nib writing tools include, for instance, a cap-less writing tool described in Japanese Patent Publication No. 5-68360. In this cap-less writing tool, a sealing tube having a through hole through which a writing nib at the tip of a writing body is provided within the body, a sealing lid is swingably fitted near the tip hole of this sealing tube and, when the writing nib is placed in a retracted state, the sealing lid is closed by a string-shaped member urged by a springy member to keep the writing nib in a sealed state. Such a writing tool, as it requires neither capping nor uncapping, can provide the effect of easier use.
However, since the sealing lid is linked to the sealing tube by a hinge in the cap-less writing tool mentioned above, not only the sealing will be insufficient where the elastic force of the springy member is too small but also, even if the elastic force is large, the sealing may still be insufficient. Thus, as the side where the string-shaped member is fitted is pulled more strongly, a gap is formed near the hinge fixed to the sealing tube to make the sealing incomplete. In other words, since the direction of the force which presses the sealing lid toward the sealing tube is not in parallel to the longer axis of the writing tool, strong pulling would make the balance disturbed by the tension of the string-shaped member and the extension of the hinge to adversely affect the sealing performance.